This invention relates generally to aircraft deicing apparatus and methods and, more particularly, to apparatus and methods for applying heated propylene glycol based aircraft deicing fluids to aircraft.
The accumulation of snow or ice on the wing, tail and other surfaces of an aircraft can drastically degrade the aerodynamic performance of the aircraft. Accordingly, various apparatus and methods have been developed for removing accumulated snow and ice from critical aircraft surfaces as well as for preventing the further accumulation of snow or ice.
One well known anti-icing technique involves an application of a heated ethylene glycol based or Type I, aircraft deicing fluid ("ADF") to the aircraft. The heated Type I ADF melts the accumulated ice and snow and, because of its solubility in water and its low melting point, helps prevent the melted ice and snow from refreezing. Although effective in removing accumulated ice and snow immediately before take off, heated Type I ADF is largely ineffective in preventing further icing for more than a brief period. Accordingly, it is not well suited for protecting aircraft that will remain on the ground in icing conditions for several minutes or hours following deicing.
To provide effective protection against the accumulation of ice and snow when an aircraft stands idle for more than brief periods in icing conditions, propylene glycol based, or Type II, aircraft deicing fluids have been developed. These commercially available Type II ADF's typically include various additives that enhance the pseudo-plastic nature of the propylene glycol fluid. The result is a viscous ADF that, when used alone or in solution with water, forms an adherent, protective film on aircraft surfaces that guards against the further accumulation of snow and ice while the aircraft is stationary, but that loses viscosity and shears away from the surfaces under the shearing force of the relative wind during the takeoff roll.
Like Type I ADF, Type II ADF can be heated to permit the removal of already accumulated ice and snow from an aircraft. However, because of its complex chemical structure and the presence of the various chemical additives, Type II ADF is easily damaged by excessive heat. Care must be taken to avoid damaging the fluid during heating. Heretofore, indirectly heated fluid-to-fluid heat exchangers have been used to ensure that the Type II ADF is heated uniformly without any "hot spots" that can cause localized burning or degradation of the Type II ADF. Although effective, such heat exchangers are complicated, expensive, prone to breakdown and difficult to repair.
In view of the foregoing, it is a general object of the present invention to provide a new and improved apparatus and method for applying heated Type II ADF to an aircraft.
It is a further object of the present invention to provide a new and improved apparatus and method for applying heated Type II ADF to an aircraft wherein degradation of the Type II ADF during and after heating is avoided.
It is a still further object of the present invention to provide a new and improved, heated, Type II ADF deicing apparatus and method that is simple, reliable and economical in construction and operation.
It is a still further object of the present invention to provide a new and improved, heated, Type II ADF deicing apparatus and method that does not involve the use of indirectly fired, fluid-to-fluid heat exchangers.